• Added a setup guidance page (setup.html) that opens when native messaging fails (e.g., desktop app not installed or not
  running). Previously, the error was only logged to console.error with no user feedback.
• The setup page guides the user to install the desktop app from the Microsoft Store and enable browser support. It includes a
  Retry button to re-test connectivity.
• Rate limiting prevents the setup page from opening repeatedly on rapid clicks (10s cooldown).
• Added i18n strings for the setup page (English + Simplified Chinese).

Note: This extension requires a native messaging host registered by the Easydict desktop app. Without it, clicking the context
menu item will open the setup page — this is the intended behavior for first-time users who haven't completed setup. The
extension does not auto-open any pages on install; the setup page only appears in response to a user-initiated action (context
menu click) that fails.